In general, this invention relates to a removal device for a biological occlusion and more particularly to a catheter and occlusion engaging element which is adapted to the removal of blockages in hemodialysis grafts.
There are many techniques and devices known in the art for removing blockages in the vascular system and other passageways of the human body.
There is a continuing need for improved devices to meet at least the following objectives.
The first objective is to reduce cost. This is particularly important in recent years where it is clear for safety and sanitary reasons that these will be single use devices. A device, even though it performs a function in some improved manner, will not be widely used if it is considerably more costly than the alternatives available.
A second objective is to provide a device that is simple to use and in a very real sense simple to understand. This will encourage its adoption and use by medical personnel. It will also tend to keep cost low.
The third objective is to provide a device that entails a procedure with which the medical profession is familiar so that the skills that have been learned from previous experience will continue to have applicability.
A fourth objective relates to the effectiveness and thoroughness with which the blockage is removed. It is important that a maximum amount of the blockage be removed; recognizing that no device is likely to provide one-hundred percent removal.
A fifth objective concerns safety; a matter which is often so critical as to trump the other considerations. It is important to avoid tissue trauma. In many circumstances, it is critically important to avoid breaking up a blockage in a fashion that leads to flushing elements of the blockage throughout the body involved.
There are trade-offs in design considerations to achieve the above five interrelated objectives. Extreme simplicity and a very simple procedure might over compromise safety. Addressing all of these considerations calls for some trade-off between the objectives.
Accordingly, a major object of this invention is to provide an improved removal device for a body passageway blockage which achieves the objectives of reduced cost, enhanced simplicity, a standard procedure, high effectiveness and a high degree of safety. Most particularly, it is an object of this invention to achieve these objectives with an enhanced trade-off value for the combined objectives.
In brief, one embodiment of this invention is particularly adapted to the removal of blockages in hemodialysis grafts. That embodiment combines a catheter having a blocking feature that blocks the annulus between the catheter and the graft and a support wire having an occlusion engaging element.
The support wire extends through the catheter, through or around the occlusion and at its distal end has an annular braided element attached thereto. The support wire is a dual element support wire having a core and an annular shell that slides on the core. The distal end of the core is attached to the distal end of the annular braided element and the distal end of the shell is attached to the proximal end of the annular braided element. Thus movement of the core and shell relative to one another moves the braided element from a radially retracted position which is useful for insertion through the catheter to a radially expanded position which expands it to the sidewall of the graft. When the annular braided element is in its radially compressed state, it can be passed through the occlusion together with the rest of the wire to reside on the distal end of the occlusion. When the braided element is expanded and moved proximally (that is, in a retrograde fashion), it will engage the occlusion and force the occlusion into the catheter. Alternatively, no motion of the engaging element may be required if aspiration is applied. In this case, the engaging element acts as a seal to prevent the suction from aspiration to remove much material beyond its point of deployment in the channel.
The distal end of the catheter is proximal of the occlusion and contains a blocking mechanism that extends radially from the distal end of the catheter to the wall of the graft or body passageway. This catheter blocking element also has a radially retracted insertion state and a radially expanded blocking state. The blocking element is a multi-wing malecot type device which is covered by a thin elastomeric film or membrane.
This malecot type of device is bonded to the distal end of the catheter or an integral part of the catheter. The distal tip of the dilator, over which the catheter is inserted, has a slightly increased diameter. This tip is in the nature of a ferrule. When the dilator is removed, the ferrule abuts against the distal end of the multi-wing malecot pushing this blocking element from its radially compressed state into its radially expanded state. Alternatively, the tip of the dilator can be bonded to the catheter with a break-away bond so that when the dilator is removed, the blocking element is expanded in a similar fashion. In this radially expanded state, the malecot and its film cover blocks the annulus around the catheter so that the occluded blood or other obstruction which is being removed is forced into the catheter where it is aspirated or otherwise removed.
Conversely, it is understood that the blocking element could be fabricated from tubular braid and the engaging element could be formed from the malecot style configuration.